The intellectual focus of the proposed University of California, Irvine (UCI), MRRC is plasticity of neural and behavioral systems as an approach to MRDD. Neural plasticity is the process by which the nervous system is altered by genes, experience, and disease. The proposed MRRC will emphasize basic research relating to plasticity of central nervous system development and clinical research relating to disordered plasticity in MRDD. UCI is recognized within the neuroscience community for developing and fostering the concept of neural plasticity. Over the past 17 years,. UCI also gained recognition for the parallel development of clinical research in mental retardation, acknowledged by the visibility of the programs in the diagnosis and treatment of MRDD. The proposed MRRC will formally recognize the confluence of these two approaches. The Center will provide core support for the investigators and promote new collaborations that will increase the breadth and scope of the research. The goals of the proposed MRRC will be to: (1) foster interdisciplinary research focused on MRDD; (2) support these research efforts through a system of resource cores that will a) ensure technological support in information processing and database management, b) provide comprehensive neurodevelopment assessment support via culture-fair, laboratory-based techniques, and c) employ molecular biology methodology to identify with greater precision the biological bases of neural plasticity; (3) promote communication among the participating clinical and basic scientists, their students and fellows, the broader university commnunity, and the public; (4) conduct initial explorations of the multicultural/multiethnic aspects of MRDD, and (5) facilitate collaboration among Centers studying related problems at UCI and other MRRCs nationally.